It has become known to carry out such coatings of a glass surface, in particular of rolled flat glass, by spraying on a solution of metal chlorides in organic acid with the free presence of atmospheric oxygen. For example, trivalent ferric chloride (FeCl.sub.3) is for this purpose dissolved at boiling temperature in pure acetic acid. However, the disadvantage of this known method lies in that due to the contact of atmospheric oxygen with the solution already during its manufacture and before it reaches the nozzle, nascent hydrochloric acid is formed in the lines to the nozzle and in the nozzle, which acid causes corrosion and destruction of the container, the lines and the nozzle. In particular, the nascent hydrochloric acid also causes a change of the color effect, which is to be effected by the solution, through which an evenness in the degree of coloring cannot be assured.
Furthermore the glass surface is exposed to different thermal currents and radiates heat, which, however, during and after the application of the solution is required for the complete oxidation of the organic acid and for the diffusion of the released metal ions, from which in the exchange alkaline ions exit. This too causes unevennesses in the degree of coloring. Due to these disadvantages, it is not possible to employ a method with metal chlorides dissolved in an organic acid to cause a glass to be made unpermeable to ultraviolet (UV) or infrared radiation, without the permeability for the visible light spectrum also being considerably influenced. Also it has not been possible up to now to manufacture a coating which is sufficiently resistant with respect to cleaning by means of alkaline solutions.
Since in the case of conventional devices irregularities in the degree of coloring are caused by the solution not being sufficiently evenly sprayed on, the further basic purpose of the invention is to provide an apparatus in which in a simple manner the spray nozzles are adjustable through which the spraying characteristic can be changed.
The basic purpose of the invention is thus to provide a method and an apparatus through which the listed disadvantages of conventional methods or conventional apparatus are overcome. Thus a method is provided wherein, by using metal chlorides which are dissolved in organic acid, coatings applied to hot glass surfaces are possible without causing a corrosion of the metal parts of the coating device and without causing the glass to have different degrees of coloring.
This is inventively achieved by the manufacture and the conveying of the coating liquid to the coating nozzle without access to oxygen. The containers for receiving the coating liquid are preferably under the pressure of an inert gas. Furthermore the chemicals are preferably moved into the container for the coating liquid through airtight conveying channels.
In an inventive apparatus for carrying out this method, a device is provided for manufacturing the coating liquid under a condition excluding oxygen and from which manufacturing device a coating device can be fed. The coating device can thereby include a bar having a plurality of coating nozzles, which bar is surrounded by a hoodlike shield, and can be rotated about a longitudinally extending axis. Furthermore the nozzles which are arranged in the bar are adjustable to different positions.
According to further preferred characteristics, thermoshields which are constructed with heating devices are provided in the area of the edge of the coating zone and the bar has a liquid-cooled housing, whereby same can be formed by two double-wall parts which are U-shaped in cross section. Finally air nozzles can be provided next to the thermoshields.